A draft created by a moving vehicle is a wake of air defining a series of cyclones spaced behind the vehicle. These cyclones, commonly referred to as vortices, increase or decrease the airspeed of a trailing vehicle. Vortices can be evidenced in some situations by dust that is swept into the vortices beside and behind a moving vehicle. An ill effect of a draft created by a lead vehicle is a reduction in fuel efficiency. Because a draft is not visually perceptible, a draft is often unnoticed by a driver. Thus, a draft can cause a reduction in fuel efficiency without the driver being aware of such reduction.
Significant fuel savings can be achieved by a trailing vehicle when the spacing between the trailing vehicle and the lead vehicle is such that a vortex is reducing headwinds as opposed to increasing the same. In order to ensure that an optimal spacing is achieved, a sensitive method of measuring and displaying the difference between the air speed and ground speed of the trailing vehicle is desired.
Several devices have been produced to measure and display air speed, especially in association with aircraft. Typical of the art are those devices disclosed in the following U.S. Pat. Nos.:
______________________________________ U.S. Pat. No. Inventor(s) Issue Date ______________________________________ 3,585,859 R. V. DeLeo, et al. Jun 22, 1971 3,618,388 R. E. Rose Nov 9, 1971 3,686,944 M. Mollick Aug 29, 1972 3,745,823 C. M. Hunter Jul 17, 1973 4,987,542 V. T. Tran Jan 22, 1991 5,091,871 J. P. Arethens Feb 25, 1992 5,104,063 J. M. Hartley Apr 14, 1992 5,119,673 V. T. Tran, et al. Jun 9, 1992 5,182,146 R. S. O'Hara Jan 26, 1993 5,259,431 R. J. Housiaux Nov 9, 1993 ______________________________________
Of these devices, those taught by DeLeo, et al. ('859), Rose ('388), Mollick ('944), and Hunter ('823) are provided for determining the airspeed of an aircraft. Such devices are not equipped to determine ground speed in order to determine a difference between the ground and air speeds for ultimately determining an ultimate spacing between a lead and a trailing vehicle.
Those devices taught by Tran ('542) and Tran, et al. ('673) are provided for determining the effects of crosswinds on a vehicle. Such devices are typically employed in the development of a particular body style of a vehicle such that the ill effects of crosswinds are reduced. These devices do not provide a driver with data to help increase fuel efficiency with respect to draft currents created by a leading vehicle.
O'Hara ('146) teaches a decorative air speed indicator. This device is placed on the hood of a vehicle and serves the dual function of a hood ornament and an air speed indicator. This device is not provided for comparing air and ground speeds for fuel efficiency purposes.
Arethens ('871) teaches a method for determining the mean wind speed with respect to the ground during the flight of an aircraft. This method does not determine ground speed, nor does is compare the determined air speed with the ground speed.
Finally, those devices taught by Hartley ('063) and Housiaux ('431) are provided for determining ground speed of an aircraft. These devices rotate the wheels associated with the landing gear at the determined ground speed such that when the aircraft touches down, skidding of the tires is minimized, thus extending the longevity of the tires and other components of the landing gear. These devices do not serve to compare air speed and ground speed.
Therefore, it is an object of this invention to provide a means for measuring a difference between the air speed and the ground speed of a motor vehicle.
It is also an object of the present invention to provide a means for displaying the determined difference between the air speed and the ground speed of the motor vehicle to the driver of the vehicle such that optimal spacing between a leading vehicle and a trailing vehicle with regard to fuel efficiency may be determined.